The invention relates to a syringe having a protective sleeve for preventing injury and possible disease caused by accidental contact with a needle mounted to the syringe.
Syringes are commonly used for the administration of medicinal liquids, anesthetics and other substances. In view of the possibility that the patient receiving an injection may be suffering from an infectious disease, it is extremely important to insure that the needle used for such injection does not subsequently wound another person.
Hypodermic needles and syringes are usually prepackaged with a shield which protects the needle and the user prior to administration of the substance to be injected. While the shield provides adequate protection prior to injection, disposal of the needle subsequent thereto has posed significant risks for doctors, nurses and other personnel. Reinstallation of the shield presents the greatest risk as improper centering of the needle with respect thereto can easily result in the sticking of one of the fingers holding the shield. Gloves do not provide adequate protection against such accidents. Recent studies have indicated that as many as 800,000 accidental needle sticks occur within each twelve month period.
Various attempts have been made to minimize the possibility of injury from hypodermic needles and the like. For example, U.S. Pat. No. 4,702,738 discloses the use of a sheath which is slidably mounted to a syringe barred and is irreversibly locked in a position covering the needle after the syringe has been used. U.S. Pat. No. 4,738,663 discloses a hypodermic syringe having a sleeve which is slidably mounted to the syringe barrel and movable between extended and retracted positions.
Certain types of syringes, such as dental anesthetic syringes, are relatively expensive and accordingly are not discarded after being used to inject a patient. The needles used in connection therewith are, of course, discarded once the patient has been anesthetized, but the syringe itself is sterilized in an autoclave.
Such local anesthetic syringes provided by most major manufacturers include a housing containing a first spring-loaded plunger, a cylindrical enclosure extending from the housing and having one or more elongate openings therein and an internally threaded opening at one end thereof, and a second plunger extending through the first plunger. The second plunger includes a handle member secured to one end thereof. A cylindrical cartridge may be loaded into the enclosure by withdrawing the spring-loaded plunger into the housing and inserting the cartridge through the elongate opening. A double-ended needle assembly is mounted to the internally threaded end of the enclosure prior to loading the cartridge. One end of this needle assembly accordingly pierces the cartridge once the spring-loaded plunger is released. The other end of the needle is protected by a sheath until the syringe is used.
Once the patent has been sufficiently anesthetized, the sheath is again mounted to the needle assembly, a procedure which entails the same risks as those associated with other syringes. The cartridge is removed by withdrawing, the spring-loaded plunger and pushing it through the elongate opening in the cylindrical enclosure.
The usual construction of non-disposable syringes having removable cartridges does not lend itself to the application of conventional protective sleeves and sheaths, which would preclude access to the cartridge whether in extended or withdrawn positions. In addition, none of these protective sleeve assemblies are readily adaptable for use on existing syringes which are not originally equipped to use such assemblies.